Idle carb sync

Started by Lead_Deficiency, September 01, 2005, 06:03:50 PM

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Lead_Deficiency

I was checking the sync today and found that @ revs the sync is dead on, but at idle the front cylinder pulls more than the rear.

Should I be concerned about this or is there a suggested fix.

I've never been impressed with the way the bike starts once it is warm, but starts great when cold. I often find myself adjustiing the idle speed screw, but I think the spring is just soft.


Lucky

I have heard of people adjusting the synq while holding the carbs at a higher RPM, but i've never seen or heard of any manual or dealer advising to do it at anything other than idle. it's how i do it & the bike runs great...
1982/3 XZ550 Touring Vison, Gold on Black

Walt_M.

Carb synch is done at idle, 1300RPM on the Vision. If you can't get the synch correct, there may be something else wrong. Valve adjustment?
Whale oil beef hooked!

Lead_Deficiency

 I set the sync @idle, the rod adjustment was so close it was almost not worth tryiing to adjust it.

The valve clearances was a good sugestion, I can't hear any ticking but maybe they should still be checked (16,000 miles on bike0, I don't know when it was done by the previous owner - sounds like a winter project.

Rick G

It depends on which  scool you come from  I've always syncd  at 2500 rpm ,  on any bike . You don't spend much time at idle  !
Rick G
Go soothingly on the grease mud, as there in lurks the skid demon
'82.5 Yamaha XZ550 RJ  Vision,
'90 Suzuki VX800, 1990 Suzuki DR350.
'74  XL350   Honda , 77 XL350 Honda, 78 XL350 Honda, '82 XT 200 Yamaha, '67 Yamaha YG1TK, 80cc trail bike

Lead_Deficiency

Yes, thats was what I was thinking to. I was going to take another shot at it.  - you've been awol for a while rick.

Coil Coyle

Rick,
You don't start the engine at 2500 RPM either.

I agree with Walt, synch at idle and adjust the valves.

$00.02

coil

silicon_toad2000

Lead, whichever way you decide to go, at idle or at revs, when you change the revs the synch will change, the cylinders don't have the same efficiency as they have different exhausts, and have different intake timing while sharing the same airbox.
Personally I think do the synch at idle, generally your idle mixtures are set the same (so many turns out) so both carbs need the same amount of vacuum to suck the same amount of fuel. At speed the kind people at yamaha have allready allowed for the difference in vaccuum with the different jet sizes in the front and rear carbs.
One mans clunker is another mans blank canvas.

Lead_Deficiency

Well lots of opinions, seems they all make sense.  ??? That larger rear jet has to be there for a reason.

Who was it that used an exhaust gas analyser to check their bike? wonder what their set up is like.

I could almost smell another poll

Rick G

I didn't "invent " syncing at 2500 . It was revealed  to me by a tech at YIC.  I've talked to several  "senior" wrenchs about it and the concesis is to sync at 2500, or there abouts.
Rick G
Go soothingly on the grease mud, as there in lurks the skid demon
'82.5 Yamaha XZ550 RJ  Vision,
'90 Suzuki VX800, 1990 Suzuki DR350.
'74  XL350   Honda , 77 XL350 Honda, 78 XL350 Honda, '82 XT 200 Yamaha, '67 Yamaha YG1TK, 80cc trail bike

Rick G

Hi lead , yes i have been absent . we moved oul moble home to  a lot , as opposed to  a moble home park. and had no utilities for a while , still don't have gas yet. Also my wife has been very ill  and in the hospital  , so I have been pretty bus, thanks  for thinking of me. .
Rick G
Go soothingly on the grease mud, as there in lurks the skid demon
'82.5 Yamaha XZ550 RJ  Vision,
'90 Suzuki VX800, 1990 Suzuki DR350.
'74  XL350   Honda , 77 XL350 Honda, 78 XL350 Honda, '82 XT 200 Yamaha, '67 Yamaha YG1TK, 80cc trail bike